The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
There are several different types of eye movements. Eye movements that allow us to quickly redirect our line of sight are referred to as saccades or saccadic eye movements. Saccades are rapid and ballistic eye movements that redirect and/or separate points of fixations, observations of a point in a visual field where the eye remains relatively still for a period of time. Fixations span about 2 degrees of the visual field, and include information which is processed with sharpness, clarity, and accuracy. In contrast, during saccades it does not appear that information is processed. Saccades, which include voluntary and involuntary changes in fixation, vary greatly in type and performance. In response to a stimulus such as light or a novel object, eye movements may include, for example, relatively slow or fast saccades, saccades that overshoot or undershoot a target or fixations, saccades with short or long latency, curved or straight saccades. Note that eye movements can distinguish between observers as well as have robustness within the observers. Thus, eye movements may remain consistent across different states of the same observer, e.g., fatigued, sober, or various other states.